A Passive Optical Network (PON) system is a pure media network, which avoids both the electromagnetic interference from external devices and the lightning effects, and reduces the failure rate of the lines and the external devices, it has features of high system reliability, saves fiber resources, has low maintenance costs, and is transparent to the network protocol, and it is a technology that is desired by the telecommunications maintenance department for a long time. Currently, a typical application networking of the passive optical network system is shown as in FIG. 1.
A Optical Line Terminal (OLT) device is a central office device in a passive optical network (PON) system, and it is a multi-service provisioning platform that supports both IP services and traditional TDM (Time Division Multiplexing) services. It is placed at the edge of a metropolitan area network or the exit of a community access network, respectively converges and sends access services to an IP network. It can connect with a plurality of ONUs (Optical Network Units) at the far end through an ODN (Optical Distribution Network), to implement the transmission of user data. It uses the PON port to connect with the PON port of the remote ONU through the ODN, so as to implement the information transmission and exchange between the OLT and the ONU, to communicate with the central office device with the 10/100/1000M electrical port (RJ45) or the 1000M optical port (SFP or GBIC), and to complete the information exchange between the OLT and the upper layer device. Currently, the structure of the OLT device system is shown in FIG. 2. It consists of a service board (i.e., a PON line card), a switch control board (i.e., a main control board), a backplane, an uplink board, a power supply and a fan. The uplink service is subjected to various PON protocol processing, message processing and traffic management through a passive optical network (PON) line card, and then is sent to the switch control board (main control board). The switch control board controls the communication between the line cards and controls the sending uplink port of each line card. The switch capacity of the switch control board decides the capacity and integration level of the conventional optical line terminal (OLT) device.
In order to prevent occurrence of the situation that three networks of data, telephone, television are installed in the household in the conventional residence network construction in a new access network, which results in duplication constructions and resource waste, and to simplify the network management, to reduce the maintenance costs and to adapt to more and more derivative and abundant value-added services, such as teletext, VOIP (Voice over Internet Protocol), video mail and online games, and to fully expand the range of services, whether having the capability of triple play is already a key point in deciding whether a new access technology has vitality or not. But the access network device, especially the optical line terminal (OLT) device, has a wide variety of derived single board types in the constant upgrading process, while the number of slots in a single device and the switching capacity are limited, resulting in the difficult in further enhancing the integration level of the device; moreover, different single boards cannot take full advantage of the slot bandwidth and the overall switching capacity, while the excessive bandwidth cannot be allocated to other interfaces, resulting in limitation to the access modes; especially, every upgrade and expansion of the network involves in the replacements of a large number of boards, and even the replacement of the whole device, so the upgrading preparation time is long, meanwhile the production cost and operation cost of the device are high.